Our research currently focuses on the role of membrane transport in the developmental biology of trypanosomes. By using radioactive tracers and applying a variety of methods including kinetic analysis, cell fractionation, and protein purification, we are determining qualitative and quantitative variations in membrane transport between blood trypomastigote forms and culture forms of Trypanosoma brucei and Trypanosoma lewisi. These studies are a part of a general program to define host parasite interactions at the level of membrane transport. We are describing the translocation of carbohydrates, amino acids and drugs by these parasites in terms of kinetics, specificity, co-factors and physical requirements. We are also searching for components of the translocation process. The question of how trypanosomes remove substrates from their environment is being approached by studying the proteins which couple with transport substrates. Transport and binding with differentially labeled proteins are compared under physiological conditions. Finally, we are using antibodies to probe the mechanism of transport in these organisms and to determine if transport sites are functional antigens.